FAQ
The following bug has been logged on the website:

Bug reference: 6565
Logged by: Guillaume Cottenceau
Email address: gcottenc@gmail.com
PostgreSQL version: 9.1.3
Operating system: not relevant
Description:

9.0 release notes contain:

"""
E.8.3.1.4. GEQO

Use the same random seed every time GEQO plans a query (Andres Freund)

While the Genetic Query Optimizer (GEQO) still selects random plans, it now
always selects the same random plans for identical queries, thus giving more
consistent performance. You can modify geqo_seed to experiment with
alternative plans.
"""

However, documentation up to 9.1 (pg website) say:

http://www.postgresql.org/docs/9.1/static/runtime-config-query.html#RUNTIME-CONFIG-QUERY-GEQO

"""GEQO's searching is randomized and therefore its plans may vary
nondeterministically."""

I guess this sentence is outdated now?

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  • Robert Haas at Apr 9, 2012 at 2:30 pm

    On Thu, Mar 29, 2012 at 3:36 AM, wrote:
    The following bug has been logged on the website:

    Bug reference:      6565
    Logged by:          Guillaume Cottenceau
    Email address:      gcottenc@gmail.com
    PostgreSQL version: 9.1.3
    Operating system:   not relevant
    Description:

    9.0 release notes contain:

    """
    E.8.3.1.4. GEQO

    Use the same random seed every time GEQO plans a query (Andres Freund)

    While the Genetic Query Optimizer (GEQO) still selects random plans, it now
    always selects the same random plans for identical queries, thus giving more
    consistent performance. You can modify geqo_seed to experiment with
    alternative plans.
    """

    However, documentation up to 9.1 (pg website) say:

    http://www.postgresql.org/docs/9.1/static/runtime-config-query.html#RUNTIME-CONFIG-QUERY-GEQO

    """GEQO's searching is randomized and therefore its plans may vary
    nondeterministically."""

    I guess this sentence is outdated now?
    Hmm, sounds like it. Does anyone think otherwise?

    --
    Robert Haas
    EnterpriseDB: http://www.enterprisedb.com
    The Enterprise PostgreSQL Company
  • Tom Lane at Apr 10, 2012 at 12:52 am

    Robert Haas writes:
    On Thu, Mar 29, 2012 at 3:36 AM, wrote:
    """GEQO's searching is randomized and therefore its plans may vary
    nondeterministically."""

    I guess this sentence is outdated now?
    Hmm, sounds like it. Does anyone think otherwise?
    Well, you could still argue that it's nondeterministic, but the
    nondeterminism is at least mostly hidden from users. I've removed
    that sentence and adjusted some other places to match.

    regards, tom lane

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postedMar 29, '12 at 7:36a
activeApr 10, '12 at 12:52a
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